Why is it that people believe weird things?

500 years ago, demons haunted our world, and incubi and succubi tormented their victims as they lay asleep in their beds.

200 years ago, spirits of the departed made bedside visits.

More recently, green and grey aliens began to molest people in their sleep and abduct them on to alien spacecraft.

What is going on here? Are these mysterious visitors in our world or in our minds?

They are in our minds. All experience is mediated by the brain, which consists of about a hundred billion neurons with a thousand trillion synaptic connections between them. No wonder the brain is capable of such sublime ideas as evolution and big bang cosmology.

But it also means that under a variety of conditions the brain is capable of generating extraordinary experiences that are not real.

Written by Michael Shermer and Pat Linse, The Science Behind Why People See Ghosts (and Gods, Angels, Demons, and Aliens and Why They Float, Fly, and Travel Out of Their Bodies) is a toolkit that can be used to assess the validity of such experiences. It is a freely downloadable off Skeptic.com, and we’re sharing it here too. Click the image below to download the PDFand read through it.

 Why People See Ghosts (PDF download)